This invention relates to sealant compositions and more particularly to bedding compositions for use in sealing insulated glass units to a frame or the like.
During the last several years, the use of insulating glass to improve the thermal efficiency of various building structures has become commonplace. Insulated glass units have been developed which have permitted such systems to be mass produced commercially and installed in building structures of all types.
These insulating glass units are essentially two panes of glass which have been sealed along their outer periphery with an organic sealant composition. The two panes of glass are separated along their outer perimeter by a continous, generally rectangular-shaped metal spacer tube. This metal spacer tube is usually perforated and filled with an inorganic desiccant. The perforated side of the spacer is positioned so that it is in communication with the inside of the insulating glass unit so that moisture from the inside of the unit may be absorbed by the desiccant. An organic sealant is used to bond the panes of glass to the spacer along the outer perimeter of the unit.
The insulating glass unit thus is sealed by the organic sealant from any further atmospheric moisture infiltration while the desiccant in the tubed metal spacer absorbs moisture from the interior of the unit. This design of the insulating glass unit prevents frosting and moisture condensation from occurring inside the unit during exposure to low temperatures.
During the installation of the insulating glass unit, the unit is placed into a metal or wooden frame or positioned against a mullion or the like. Prior to positioning the insulating glass unit in the frame or against a mullion, a glazing or bedding compound is applied to the frame or mullion to provide a seal between the insulating glass unit and the frame or mullion. This seal prevents air or moisture penetration through the frame or mullion and insulating glass unit interface.
There are a variety of sealants which are used in insulating glass units. At present, the most widely used insulating glass sealant is a polysulfide based polymer. These sealants are essentially formed-in-place gaskets which are produced by chemical curing via a cross-linking reaction of a liquid polysulfide base and a metallic oxide curing agent. The cross-linked nature of the sealant provides a reasonable degree of chemical resistance. Other insulating glass sealants are silicone based polymers and polyurethanes. These sealants are also chemically cross-linked, and likewise, typically have reasonable chemical resistance to a wide variety of commercially available solvent-based bedding compounds.
However, another class of insulating glass sealants are hot melt sealants such as hot melt butyl rubber sealants. Such hot melt sealants are increasing in popularity because of their high adhesion properties, low water vapor transmission, and ease of application. Unlike the above-described chemically cured insulating glass sealants that are flowed into place and solidified by a chemical cross-linking mechanism, these hot melt sealants are melted, flowed into place while hot, and form solid seals upon cooling. Such hot melt systems generally do not possess a high degree of cross-linking (if they did they would not be flowable when heated) and have limited chemical resistance. Consequently, during the glazing operation, if such hot melt systems come into contact with typical commercially available solvent-based bedding compounds, they have a tendency to soften permanently and/or lose adhesion to the insulating glass panes or the metal spacer. This results in failure of the insulating glass unit.
This incompatibility between hot melt sealants and typical solvent based bedding compounds is to be distinguished from a different compatibility problem also faced in this art, namely, initial adhesion compatibility between insulating glass sealants and bedding compounds. This latter problem has been addressed by Mistrick et al, U.S. Pat. No. 4,348,435, which teaches the application of an acrylic emulsion primer to a hot-melt butyl insulating glass sealant to promote adhesion to a silicone-based glazing compound. However, Mistrick does not address or solve the problem of long term permanent softening or loss of adhesion between hot melt sealants and bedding compounds. Moreover, the primer of Mistrick is designed only for the class of silicone-based glazing compounds and adds a further manufacturing step to the production of sealant insulating glass units.
As hot melt sealants have become increasingly more widespread in usage, there is a need in this art to provide a solvent-based bedding compound that is not only compatible with chemically cured insulating glass sealant compounds but is also compatible with hot melt systems. That is, there is a need for a bedding compound which, when in contact with an insulating glass sealant, will not unduly soften it or cause it to lose adhesion to the glass or metal spacer of the insulating glass unit.